Adding option for Proguard jar to be switched.

build/config/android/internal_rules.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
 assert(is_android)
 
 # Write the target's .build_config file. This is a json file that contains a
@@ skipping 521 matching lines @@
     action(target_name) {
       set_sources_assignment_filter([])
       forward_variables_from(invoker,
                              [
                                "deps",
                                "data_deps",
                                "public_deps",
                                "testonly",
                              ])
       script = "//build/android/gyp/proguard.py"
-      _proguard_jar_path = "//third_party/proguard/lib/proguard.jar"
+      if (defined(invoker.proguard_jar_path)) {
+        _proguard_jar_path = invoker.proguard_jar_path
+      } else {
+        _proguard_jar_path = "//third_party/proguard/lib/proguard.jar"
+      }
       _output_jar_path = invoker.output_jar_path
       inputs = [
         _proguard_jar_path,
       ]
       if (defined(invoker.alternative_android_sdk_jar)) {
         inputs += [ invoker.alternative_android_sdk_jar ]
         _rebased_android_sdk_jar =
             rebase_path(invoker.alternative_android_sdk_jar)
       } else {
         inputs += [ android_sdk_jar ]
@@ skipping 1815 matching lines @@
       outputs = [
         depfile,
         invoker.out_manifest,
       ]
       inputs = [
         invoker.main_manifest,
       ]
     }
   }
 }